1. Technical Field
The present invention relates to an apparatus and a method of manufacturing a rubber member.
2. Related Art
In general, a pneumatic tire is manufactured in such a manner that respective tire constituting members such as an inner liner, side wall portions, bead portions and a tread portion are formed in advance, a green tire is formed by laminating these tire constituting members in an unvulcanized state, and the green tire is molded by vulcanization. There may be a case where these tire constituting members are molded such that a mixed and kneaded rubber material is extruded from a mouthpiece by an extruder thus forming a rubber member having a predetermined cross-sectional shape, and end portions of the formed rubber member are bonded to each other.
In the case where the tire constitutional member is formed by joining the end portions of the rubber member in this manner, when a cross-sectional shape of the rubber member molded by extrusion is fixed, a joining portion has a large thickness compared to other portions thus giving rise to a drawback that a weight balance becomes non-uniform.
In view of such a drawback, JP-A-2013-107370 proposes an apparatus having the constitution where a rubber member is molded by extruding a rubber material to a support surface from a mouthpiece of an extruder and by rotatably moving the support surface and the mouthpiece relative to each other, wherein a rubber pool portion is formed between the support surface and the mouthpiece, an opening portion of the rubber pool portion is closed by a shutter, a rubber material ejected from the mouthpiece is filled in the rubber pool portion and, thereafter, an opening portion is opened by moving the shutter while moving the support surface and the mouthpiece relative to each other. With such a configuration, a thickness of a terminal end portion of the molded rubber member can be reduced and hence, it is possible to prevent the joining portion from having a large thickness compared to other portions.
However, the following is found with respect to the structure shown in FIG. 10, which is disclosed in JP-A-2013-107370. That is, a rubber material filled in the rubber pool portion 106 formed between the support surface 102 and the mouthpiece 104 intrudes into a slight clearance formed between the support surface 102 and the shutter 108 thus forming a rubber film portion m0 having a small thickness at a starting end ms of the rubber member m as shown in FIG. 11. However, there may be a case where a thickness of the rubber film portion m0 is sharply increased thus forming the starting end ms having a large change in film thickness due to the movement of the shutter 108 toward an open position. Although a gentle change in thickness may be acquired by reducing a moving speed of the shutter 108, it is not always easy to control a change in thickness based on a moving speed.